1. Field of the invention
The present invention concerns a process for the production of an organic electrolyte electric cell with a unitary structure.
2. Description of the prior art
A cell with a unitary structure is a cell in which the elements constituting it, in particular the electrodes and the separator, are integral so that each element follows all of the dimensional variants of the cell during its operation.
A number of prior art documents propose a process for the production of a cell with a unitary structure which uses a plasticizing additive during assembly of the elements of the cell.
U.S. Pat. No. 5,456,600 describes a process for the production of a cell with a unitary structure which consists of adhering the cell elements, namely the electrodes, the separator and optionally the collectors, by rolling. Each element of the cell is in the form of a polymeric film, preferably based on a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVDF-HFP). The separator and optionally the other elements of the cell contain a plasticizer which conserves the microstructure of the elements during rolling. The plasticizer is then eliminated by extracting it with a selective solvent.
In U.S. Pat. No. 5,540,741, a first electrode is constituted by a conductive support on which a paste containing a polymer, a plasticizing additive and an electrochemically active material are deposited. The polymer is preferably a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVDF-HFP). After drying, the electrode is coated with a film which constitutes the separator. The electrode-separator assembly is then coated with a second electrode and heated under pressure.
The plasticizer is then extracted using a solvent which is inert towards the polymer.
U.S. Pat. No. 5,552,239 describes the same process as above using other polymers, such as polyvinyl chloride, acrylonitrile/butadiene copolymers and polyacrylonitrile polymers, to constitute the separator.
The three processes described above have the advantage of allowing the cell to be assembled in the open air. However, the plasticizer extraction step is lengthy and difficult.
The aim of the present invention is to provide a process for the production of an organic electrolyte electric cell with a unitary structure:
which comprises a limited number of simple steps; PA1 which does not use a long and complex extraction step; and PA1 which can produce a cell with minimal dimensional variants. PA1 a first electrode comprising the superposition of a first layer containing an electrochemically active material and a porous second layer of a polymeric material having a free face; and PA1 a second electrode comprising a porous layer having at least one free face and containing an electrochemically active material; PA1 functions as the seat of the electrochemical reaction, which uses the electrochemically active material contained in the first layer; PA1 functions as the electrical separator to prevent any contact between the active material of the first electrode and that of the second, which is ensured by the second layer constituted by a polymeric material selected for its electrical insulating properties; and PA1 functions as a reservoir for the electrolyte since the second porous layer is constituted by a polymeric material which has a physicochemical affinity for the electrolyte. PA1 a polymer with the same chemical formula as the polymer constituting the second porous layer of the first electrode; PA1 a solvent in which the polymer readily dissolves at the adhesive preparation temperature; and PA1 a non-solvent which is miscible with the solvent, which does not or only slightly dissolves the polymer at the adhesive preparation temperature and the proportion of which is insufficient to cause precipitation of the polymer.